Abstract

Cooler temperatures exacerbate chikungunya viral arthritis.

Inflammatory arthritis patients often claim that changes in weather give them aches and pains, which may cause friends and family to raise their eyebrows. However, a recent study by Prow et al. may have found a link between joint inflammation and temperature. In 2014, a mosquito-transmitted alphavirus called chikungunya virus (CHIKV) spread quickly across the islands of the Caribbean and into Central and South America, infecting millions of people. CHIKV causes fever during the first few days after infection and subsequently invades the joints, causing severe joint swelling and pain. Many patients infected with CHIKV are so debilitated by pain that they are unable to walk during the first week after infection, and up to 60% of patients experience chronic joint pain that lasts many months or even years.

Prow et al. hypothesized that temperature may impact the severity of CHIKV arthritis, so they directly tested this hypothesis in mouse model of the disease. Mice that were housed in a warm environment (30°C) had less severe arthritis; diminished viral titers in the blood, spleen, lymph node, and muscle; and a more robust antiviral type I interferon (IFN) response when compared with mice housed at the standard 22°C. Similar temperature-dependent effects also were observed in studies of Ross River virus, a CHIKV-related arthritogenic alphavirus.

A great mystery in rheumatology is why certain forms of inflammatory arthritis (e.g., rheumatoid arthritis, psoriatic arthritis) affect particular joints and not others. Like patients with rheumatoid arthritis, CHIKV arthritis frequently affects peripheral joints involving the hands and the feet. The finding that CHIKV thrives at lower temperatures may explain why distal joints are more frequently affected in patients with CHIKV arthritis. Furthermore, the concept that temperature modulates the type I IFN response may prompt further studies of rheumatologic disease that help to explain the old notion that arthritic joints can detect weather changes.